SDL: testmessage: Create a renderer for window display on Wayland

From 1cd97e26958fb141088c66d93e32ab91ac0e1854 Mon Sep 17 00:00:00 2001
From: David Gow <[EMAIL REDACTED]>
Date: Mon, 29 Mar 2021 18:12:33 +0800
Subject: [PATCH] testmessage: Create a renderer for window display on Wayland

On Wayland -- or at least on some Wayland implementations -- windows
aren't shown until something has been rendered into them. For the
'testmessage' test program, this means that the final messagebox (a
modal one) is blocking an "invisible window", which can then be
difficult to close.

By creating a renderer and presenting once, the window is properly
displayed, and the test behaves as it does under X11 (including
 test/testmessage.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test/testmessage.c b/test/testmessage.c
index 9693e4e64..a93ad7027 100644
--- a/test/testmessage.c
+++ b/test/testmessage.c
@@ -189,6 +189,12 @@ main(int argc, char *argv[])
         SDL_Event event;
         SDL_Window *window = SDL_CreateWindow("Test", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, 0);
+        /* On wayland, no window will actually show until something has
+           actually been displayed.
+        */
+        SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, 0);
+        SDL_RenderPresent(renderer);
         success = SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
                     "Simple MessageBox",
                     "This is a simple error MessageBox with a parent window",